Control systems and methods for electric motors of utility vehicles

ABSTRACT

Electronic control systems and related control methods for controlling electric auxiliary motors for performing work, such as electric deck motors for mower blades. The apparatus is shown in use with a vehicle that includes a mowing deck. Features of the control systems allow for safe and efficient use of the vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/041,589, filed Sep. 30, 2013, which is a continuation of U.S. patentapplication Ser. No. 13/618,270, filed Sep. 14, 2012, now U.S. Pat. No.8,548,694, which is a continuation of U.S. patent application Ser. No.13/290,914, filed Nov. 7, 2011, now U.S. Pat. No. 8,296,003, which is acontinuation of U.S. patent application Ser. No. 12/605,226, filed Oct.23, 2009, now U.S. Pat. No. 8,055,399, which claims the benefit ofProvisional Application Ser. No. 61/107,987, filed Oct. 23, 2008 andProvisional Application Ser. No. 61/155,749, filed Feb. 26, 2009. Eachpatent application identified above is incorporated herein by referencein its entirety to provide continuity of disclosure.

TECHNICAL FIELD

This disclosure is generally related to utility vehicles, such as lawnand garden tractors and mowers, and more particularly to controlsystems, methods and processes for primary and auxiliary electric motorpower systems.

BACKGROUND OF THE INVENTION

Utility vehicles, such as, for example, lawn and garden tractors andmowers, generally rely upon internal combustion engines as the primemover transferring power through mechanical linkages (gearing or belts),hydrostatic drive(s) or other similar devices to propel or drive thevehicle. A deck of the utility vehicle is typically used to employ anauxiliary system, such as cutting blades of a lawn tractor. The majorityof commercial and consumer mowers employ a deck (auxiliary) drive systemusing belts and pulleys driven by an engine typically with an electricclutch/brake to stop or drive the deck system. Other variants take theform of a power take off shaft in combination with pulleys and belts todrive multiple blade spindles in larger decks or to individually drivespindles with hydraulic motors in multiple deck or reel versions.

Utility vehicles incorporating electric motor(s) as primary mover(s)have emerged as viable alternatives to internal combustion utilityvehicles, particularly due to rising oil and fuel prices. Consumers alsowant products with increased comfort and increasing versatility insmaller packages. Electric vehicles offer considerable advantages forreduction of emission of noise and pollution, as well as improvedoperator controls. These vehicles, which typically include one or morework accessories or auxiliary systems incorporating additional electricmotors, also incorporate various forms and levels of control, dependingupon the vehicle type, drive type, functional features, and other designaspects to ensure safe operation. With the advancement of these vehicletypes and their functionality, various problems and needs have arisen intheir design, operation, and functionality.

This disclosure is directed to addressing various problems, needs, andimprovements in the general area of primary and auxiliary controlsystems and methods relating to utility vehicles.

SUMMARY OF THE INVENTION

Electronic control systems and related control methods and features forcontrolling electric motors of primary and auxiliary systems of utilityvehicles or other utility power equipment. In exemplary embodiments,control systems and related control methods are disclosed in connectionwith auxiliary motors in the form of deck motors associated with amowing deck of a mowing vehicle.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forth anillustrative embodiment and is indicative of the various ways in whichthe principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting an overview of general controlsystem architecture applicable to a vehicle contemplated by theprinciples of the present invention.

FIG. 2 is a top plan view of a first embodiment of a vehicle in the formof a riding lawn mower to which one or more principles or aspects of thepresent invention may be applied.

FIG. 3 is a block diagram of an embodiment of a control systemapplicable to a vehicle such as the vehicle depicted in FIG. 2.

FIG. 4 is a block diagram of another embodiment of a control systemapplicable to a vehicle similar to that depicted in FIG. 2, butincorporating a steering wheel.

FIG. 5 is a top plan view of a second embodiment of a vehicle in theform of a riding lawn mower to which one or more principles or aspectsof the present invention may be applied.

FIG. 6 is a block diagram of an embodiment of a control systemapplicable to a vehicle such as the vehicle depicted in FIG. 5.

FIG. 7 is a block diagram of a deck controller in accordance with theprinciples of the present invention.

FIG. 8 is a block diagram of the left (master) controller depicted inFIG. 7 in accordance with the principles of the present invention.

FIG. 9 is a block diagram of the right (slave) controller depicted inFIG. 7 in accordance with the principles of the present invention.

FIG. 10 is a control function block diagram illustrating electric motorcontrol for each of the deck motors.

FIG. 11 is a bubble state map depicting the operational statesassociated with control of the electric deck motors.

FIG. 12 illustrates flow charts of a main program flow associated withthe deck controller.

FIG. 13 is a general schematic diagram of a 3-phase bridge generallyrepresenting the type utilized in connection with pulse-width modulationto generate motor current to drive the motor.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the present invention in accordance with itsprinciples. This description is not provided to limit the invention tothe embodiments described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiments describedherein, but also other embodiments that may come to mind in accordancewith these principles. The scope of the present invention is intended tocover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers, such as, for example, in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. Such labeling and drawing practices do not necessarilyimplicate an underlying substantive purpose. As stated above, thepresent specification is intended to be taken as a whole and interpretedin accordance with the principles of the present invention as taughtherein and understood to one of ordinary skill in the art.

As referenced in FIG. 1, control systems for utility vehicles typicallyincorporate elements from four functional segments: a user interfacesegment 10, a controller/processor segment 12, a system feedback segment14, and an output segment 16. Utility vehicles may incorporate one ormore interfaces 20, such as, for example, a steering wheel, steeringlevers, an accelerator or other control pedal, a brake pedal or lever, abypass switch, a power take off (PTO) switch, visual displays or meters,etc. These user interfaces fall into one of two categories, inputinterfaces, such as a steering wheel, and feedback interfaces, such as abattery meter. Utility vehicles may also incorporate one or more sensorsor feedback architectures 22, such as, for example, speed sensors,steering sensors, accelerator sensors, temperature sensors, voltagesensors, current sensors, etc. The sensor(s) 22 and the userinterface(s) 20 are in communication with one or morecontrollers/processors 24 of the system. The controller(s) 24 utilizeinputs from one or more of the user interface(s) 20 and the sensor(s) 22in processes and algorithms and provide one or more appropriate outputs26 to various components of the vehicle. Output(s) 26 may include, forexample, control and operational signals for one or more auxiliarydevices, such as a motor for a mower blade or other implement, controland operational signals for one or more primary movers, such as anelectric drive motor, control signals to one or more additionalcontrollers, control signals to one or more drivers, signals outputtedto user interfaces such as visual displays or meters, etc.

FIG. 2 illustrates a vehicle embodiment in the form of vehicle 50 thatutilizes auxiliary devices. Vehicle 50 is a mowing vehicle thatincorporates one or more principles of the present invention. Powersupply 38 of vehicle 50 drives electric motor transaxles 40 a and 40 b,which each separately drive one of two rear wheels to implement zeroturn vehicle functionality. It should be noted that the use of the termwheel is intended to cover all types of wheels, as well as gears,linkages, or other mechanisms that may ultimately translate into afraction implement, such as, for example, an inner wheel of a trackarrangement on a track vehicle. In this embodiment, the electrictransaxles 40 a and 40 b are nested in a side-by-side, parallelarrangement as shown in FIG. 2. The electric transaxles 40 a and 40 butilize an electric motor to drive an associated axle and wheel. In aparticular embodiment, the electric fraction motor is a three phase ACinduction motor rated for 1.7 kW continuous duty. Other motors andratings, however, can be utilized. As shown in FIG. 2, vehicle 50includes user interfaces, such as right and left drive levers 36 a and36 b, an indicator LED or lamp 56, vehicle key switch 58, power take-off(PTO) switch 60, cruise switch 62, brake switch 66, battery gauge 70,and hour meter 72.

In the embodiment illustrated in FIG. 2, vehicle 50 incorporates a pairof traction controllers 29 a and 29 b and a deck controller 30. In thisparticular embodiment, the traction controllers 29 a and 29 brespectively control electric transaxles 40 a and 40 b, and when certainoperational conditions are met, allow the operator of vehicle 50 toclose PTO switch 60 to energize or allow activation of one or morefunctional outputs controlled by the deck controller 30. Thesefunctional outputs may include a variety of auxiliary equipment poweredby electric auxiliary motors, such as deck motors 34 a and 34 b of mowerdeck 35 (illustrated), or in other embodiments, a snow thrower, atiller, sweeper brooms, or other implements. In a particular embodiment,the deck motors 34 a and 34 b are electric motors in the form ofpermanent magnet synchronous motors (PMSMs). In another particularembodiment, the electric motors are 1.5 kW rated for continuous duty orpower. Other motors and ratings, however, can be utilized. For example,a brushless DC (BLDC) motor may also be utilized.

In the embodiment of FIG. 2, the deck controller 30 controls deck motors34 a and 34 b of the deck 35 of the vehicle 50. As will be described inmore detail herein, in some embodiments the deck controller may comprisea pair of controllers to respectively control the deck motors 34 a and34 b. In other embodiments, a single deck controller may be employed tocontrol both deck motors 34 a and 34 b. The deck controller 30 ismounted to the deck or frame of the vehicle and is capable of electricalcommunication with the traction controllers 29 a and 29 b and the deckmotors 34 a and 34 b. As already noted, in this particular embodiment,each of the deck motors are permanent magnet synchronous motors (PMSMs),however, other motor types may be implemented as well. In thisembodiment, each of the deck motors has a blade that is directly coupledto its rotor such that the rotational speed of the rotor is also therotational speed of its respective blade. In other embodiments, areduction feature may be implemented, such as by gears or via directcontrol of the electric motor, to optimize rotational speed associatedwith the auxiliary equipment.

FIG. 3 illustrates an embodiment of the functional relationship andcommunication between various components of a control system inaccordance with one or more principles of the present invention, whichcan be adapted to vehicle 50. As illustrated in FIG. 3, a mastertraction controller 290 a and a slave fraction controller 290 bcommunicate with each other with respect to status and values relatingto various components and interfaces of the control system and thevehicle. Preferably, the master and slave fraction controllers 290 a and290 b communicate via a CAN bus or other bus type or communicationstandard. Additionally, master traction controller 290 a is in directcommunication with transaxle 292 a and slave fraction controller 290 bis in direct communication with transaxle 292 b. Master fractioncontroller 290 a also communicates with a master deck controller 294preferably via CAN bus 288, which in turn communicates with slave deckcontroller 295, preferably via SPI bus 289. Both master and slavecontrollers respectively control right and left deck motors 296 a and296 b. A right drive lever position sensor 291 a is associated with theright drive lever and is in communication with the master fractioncontroller 290 a. Similarly, a left drive lever position sensor 291 b isassociated with the left drive lever and is in communication with theslave traction controller 290 b. Other operator interfaces 298, such as,for example, key on/off, PTO, ROS, cruise, and brake, are incommunication with fraction controllers 290 a and 290 b.

FIG. 4 illustrates another embodiment of the functional relationship andcommunication between various components of a control system inaccordance with one or more principles of the present invention, whichis also adaptable to vehicle 50. In this particular embodiment, asteering wheel is utilized to effectuate steering for a zero turnvehicle arrangement via master and slave traction controllers, and amaster motor controller and a slave motor controller are configured tocontrol a pair of auxiliary motors in the form of deck motors, whichdrive mower blades. As illustrated in FIG. 4, a master tractioncontroller 490 a and a slave fraction controller 490 b communicate witheach other in a manner similar to controllers 290 a and 290 b of FIG. 3.Master fraction controller 490 a also communicates directly withtransaxle 492 a and slave traction controller 490 b communicatesdirectly with transaxle 492 b. Master traction controller 490 a alsocommunicates with a master motor controller 494, preferably via a CANbus 488 (or other bus type or communication standard). In the particularembodiment illustrated, the master motor controller 494 communicateswith auxiliary motor 496 a and slave motor controller 495 via SPI bus489. Slave motor controller 495 communicates with auxiliary motor 496 b.Operator interfaces 498, such as, for example, key on/off, PTO, ROS,cruise, and brake, are in communication with traction controllers 490 aand 490 b. Master fraction controller 490 a also receives input fromsteering position sensor 491, accelerator position sensor 493, and mayadditionally receive input from vehicle and system feedback sensors 499to improve control of the vehicle.

FIG. 5 illustrates a vehicle embodiment in the form of vehicle 150 thatalso utilizes auxiliary devices, wherein the vehicle 150 utilizes asingle electric motor transaxle rather than the two electric motortransaxle embodiment of FIG. 2. Therefore, vehicle 150 includes a singletraction controller 129. Power supply 138 of vehicle 150 drives electricmotor transaxle 140, which drives an axle having rear wheels connectedthereto. It should be noted that the use of the term wheel is intendedto cover all types of wheels, as well as gears, linkages, or othermechanisms that may ultimately translate into a fraction implement, suchas, for example, an inner wheel of a track arrangement on a trackvehicle. As shown in FIG. 5, vehicle 150 includes user interfaces, suchas steering wheel 151, accelerator pedal 152, brake pedal 154, anindicator LED or lamp 56, vehicle key switch 58, power take-off (PTO)switch 60, cruise switch 62, brake switch 66, battery gauge 70, and hourmeter 72, and a reverse operating switch (ROS) 164.

As shown in FIG. 5, vehicle 150 includes a mower deck 135, whichincorporates a pair of deck motors 134 a and 134 b. A deck controller130 is in communication with the fraction controller 129 and controlsthe deck motors 134 a and 134 b. As will be described in more detailherein, the deck controller 130 may comprise a pair of controllers torespectively control the deck motors 134 a and 134 b.

FIG. 6 illustrates an embodiment of the functional relationship andcommunication between various components of a control system inaccordance with one or more principles of the present invention, whichcan be adapted to vehicle 150 of FIG. 5 or similar vehicles. In thisparticular embodiment, a traction controller 390 is implemented tocontrol functional aspects of an electric transaxle 392. Tractioncontroller 390 is in communication with a plurality of user/operatorinterfaces 398, as well as vehicle and system feedback sensors 399, andan accelerator position sensor 393. Optionally, a steering positionsensor 391 can be added to the control system to establish controlfunctionality that includes steering position parameters. The tractioncontroller 390 is also in communication with a master auxiliarycontroller 394, preferably via a CAN (Controller Area Network) bus 388.The master auxiliary controller 394 incorporates a slave controller 395,which is in communication with the master controller via an SPI (SerialPeripheral Interface) bus 389. Alternatively, all of the controllers canbe configured to communicate directly to the CAN bus.

The foregoing embodiments are capable of integrated control of vehiclefunctionality. In accordance with the system architecture, signals fromthe vehicle, user interfaces, system sensors, the deck controllers, andthe fraction controllers can be shared to create a fully integratedcontrol system. The integrated control between the tractioncontroller(s) and the deck controller(s) provides a platform fornumerous features and functionality for optimum performance and safety.

In a vehicle embodiment employing two auxiliary motors, such as deckmotors associated with cutting blades of a mowing vehicle, the deckcontroller may be configured to have a first controller and a secondcontroller, which may be integrated into one controller or may beseparate controllers. FIG. 7 depicts a logic block diagram of a deckcontroller 530 for a vehicle utilizing two deck motors. Referring toFIG. 7, the deck controller 530 comprises several components, a leftcontroller (master) 530 a, a right controller (slave) 530 b, a commoninterface 532, a bias supply/dynamic brake/contactor control 534, a leftpower inverter 536, a right power inverter 538, and a batteryconditioner 540. The deck controller 530 optionally interfaces with acontactor 550 and a dynamic brake system 552.

Referring to FIG. 8 and FIG. 9, each of the controllers 530 a and 530 brespectively include a digital signal processor (DSP) 600 a, 600 b, anoscillator 602 a, 602 b for clocking functions, an analog/digital (A/D)interface 604 a, 604 b, a program interface 606 a, 606 b, and optionaltest logic 608 a, 608 b. The A/D interface 604 a, 604 b receives inputsto the deck controller 530 a, 530 b and appropriately converts theseinputs into a digital signal for processing by the DSP 600 a, 600 b. Ina particular embodiment, the inputs to the deck controller 530 a, 530 bare supplied via a control connector connected to the deck controller530 and having eight pins and a battery input supplying 48V, DC throughthe battery conditioner 540. Three of the pins are associated with thecontroller area network (CAN)-bus, which communicate with the tractioncontroller. The three CAN-bus pins are a serial link to the CAN-bus,which comprises one transmit line, one receive line, and one ground linein a standard serial loop. Another three of the pins are associated withmotor thermistor signals, which represent the temperature of the leftand right deck motors. The thermistor signals are generated bythermistors placed in the windings of each motor. One of the pins isassociated with the contactor coil ground, which is used to turn on/offthe contactor 550. One pin is associated with an ignition switch. Thus,the inputs to the DSP generally include (1) the controller DC voltagelevel signal; (2) the PMSM current signal; (3) the hall effect ACsignals; (4) the brake over-current signal; (5) the DC motor currentsignal; (6) the controller and motor temperature signals; (7) faultinterrupt signals; (8) fault time from latches; and (9) the ignitionstatus signal.

The CAN-bus pins are capable of receiving the following information fromthe traction controller: on/off signal for communicating the on or offstate of the deck motors, speed data to control the speed of the deckmotors, and direction data to control the clockwise or counter-clockwisedirection of the deck motor rotors. In a particular embodiment, thespeed data will be fixed to one or two speeds, on or off, or high andlow speeds. In other embodiments, the speed data may be varied by a userover a broader range of speeds. The CAN-bus pins are capable ofcommunicating at least the following information to the tractioncontroller: status data, fault data, temperature data.

As illustrated in FIG. 8 and FIG. 9, each of the controllers 530 a, 530b have output control signals relating to driving/braking functions andfault/interrupt functions, both associated with their respective deckmotor. Collectively, the deck controller 530 has six outputs asillustrated in FIG. 7: three PMSM control signals to each deck motor,where each of the PMSM control signals to the left deck motor is 120degrees out of phase, and where each of the PMSM control signals to theright deck motor is also 120 degrees out of phase. The PMSM controlsignals control the speed of each deck motor.

FIG. 10 is a circuit control diagram showing both hardware components700 and software components 800 of each of the deck controllers 530 aand 530 b. It should be understood that any of the depicted componentscan be implemented through the use of software, hardware, firmware, or acombination thereof. The software components 800 are preferably residentin the DSP 600 a, 600 b, and include algorithms involved in sensorlessfield oriented control (FOC) of a PMSM motor. FOC theory allows use ofDC control techniques for an AC motor. The algorithms includeproportional/integral/derivative (PID), Park transform, inverse Parktransform, position and speed estimator using the principals of fieldoriented control to the space vector pulse width modulation (PWM), andClark transformation. Signals resulting from these algorithms areutilized by the hardware components 700. The gate drivers receive thesesignals and control the 3-phase bridge of the respective power inverter536, 538, which controls the respective PMSM. Many types of processors,inverters, programmable logic controllers (PLCs), or the like could beutilized in accordance with the principles of the present invention.Furthermore, in certain embodiments, deck controller 530, and deckcontrollers 530 a and 530 b may each incorporate more than one axiscontroller or processor, depending on the architecture implemented andother functional needs. The 3-phase bridge preferably utilizes metaloxide semiconductor field effect transistors (MOSFETs), insulated gatebipolar transistors (IGBTs), or the like.

The left and right controller 530 a, 530 b are nearly identical. Theleft controller 530 a is the master controller while the rightcontroller 530 b is the slave controller. The master controller directsthe slave controller and is in direct communication with the connectorof the deck controller 530.

As shown in FIG. 10, each of the DSPs also implements fault protectionalgorithms. Generally, these algorithms determine what actions will betaken when the left or right controller logic receives an interruptsignal. For example, the algorithms will dictate whether to shut downthe deck control and/or deck motor; to re-try the deck controller aftera pre-determined period of time; and whether to clear the respectivelatches.

The DSP also implements the Field Oriented control (FOC) algorithm. Ingeneral, the input to this algorithm is either the Hall effect ACsignals or the PMSM current signal. The FOC algorithm converts the threephases of the AC current in the respective deck motor into a DCreference frame using a Clark transform (Clarke transform), a Parktransform and a position and speed estimator that estimates the speedand the position of the rotor based, in part, on the three phases of theAC current in the respective deck motor. The DC reference frame isequivalent to the reference frame of the rotor. Once in the DC referenceframe the rotational speed and the magnetic flux of the motor can becontrolled using conventional DC control techniques. Using the inversePark and Clark transforms, the error between the desired speed andmagnetic flux can be translated into suitable six controller PWM'dcontrol signals.

Referring again to FIG. 7, the common interface 532 serves the followingfunctions: (1) rail splitting functions to generate various referencesignals for the comparators positioned throughout the deck control; (2)ignition sensing logic to sense when an ignition switch has been openedand closed and to sense when the battery voltage is in a safe operatingrange; (3) temperature fault sensing to generate when the temperature inthe left or right deck motor is too high or when the temperature in thedeck controller itself is too high; and (4) interrupt signal generationin response to certain fault conditions.

Interrupt signals are generated in response to the following recognizedfaults: (1) a temperature fault in the left or right deck motors; (2) atemperature fault associated with the left side or right side of thedeck controller; (3) an over-voltage condition as determined by theover-voltage comparator logic (from the bias supply logic, brake logicand contactor logic) and its generated over-voltage fault signal; and(4) an over-current fault during dynamic braking or contactor coiloperation as determined by the brake/contactor coil over-current faultsignal (from the bias supply logic, dynamic brake logic and contactorlogic).

The common interface logic communicates the interrupt signals to theleft or right controller logic. Temperature faults are communicated tothe left or the right controller logic based on whether the fault isfrom the left or right side. Other faults are communicated to the leftcontroller logic. The left or right controller logic receives theinterrupt signals and is capable of reading latch data corresponding tothe cause of the fault. When desired, the left or right controller logicsends a fault reset command to reset the latches after an interruptsignal is read.

Referring again to FIG. 7, the left and right power inverter areidentical to each other. Each is coupled to receive (1) reset commands(from the left and right controller logic) so that the left and rightpower inverter logic can reset its internal latches that are used toreport deck controller conditions to the left and right controllerlogic, (2) six controller PWM control signals to control sixmetal-oxide-semiconductor field-effect transistors (MOSFET) of the3-phase bridge that generate the three PMSM control signals, (3) acontroller DC voltage level signal representative of the voltage in thedeck controller (from the bias supply logic, dynamic brake logic andcontactor logic) so that the deck controller can protect the deck motorsfrom over-voltage conditions, and (4) controller thermistor signalsrepresentative of the temperature of the deck controller (fromthermistors positioned in the deck controller).

Each of the left and right power inverters output three PMSM controlsignals to respectively control each of the left and right deck motors.As noted, each of the three PMSM control signals is 120 degrees out ofphase. Each of the left and right power inverters also generates thefollowing outputs: (1) high trip over-current fault latch datarepresentative of an over-current condition in a respective deck motor;(2) a DC motor current signal representative of the DC current seen inthe deck motor; (3) hall effect AC signals representative of two of thethree AC phase currents in each Deck Motor (i.e., two of the three PMSMcontrol signals); and (4) a PMSM current signal representative of theoverall AC current seen in each deck motor. Each of the above outputs iscommunicated to the respective left controller and the right controller.The high trip over-current fault latch data is stored in an internallatch of the respective power inverter for communication with therespective controller.

The hall effect AC signals are duplicative with the PMSM current signalto the extent that each measures the same thing: the AC currents in thedeck motor for feedback to the left and right controller logic. In otherembodiments, it is possible that only one of the hall effect AC signalsand the PMSM current signal will be output from each of the left andright power inverter logic. In a preferred embodiment, the Hall effectAC signals are generated using two hall effect sensors coupled toreceive two of the three PMSM control signals before transmission to therespective Deck Motor. In a preferred embodiment, the PMSM currentsignal is generated using (1) a DC Shunt positioned to receive thereturn current from the respective deck motor and (2) correspondingshunt reading logic.

Functionally, each of the left and right power inverters is capable ofrecognizing a high trip over-current fault condition, a low tripover-current fault condition and an over-voltage condition. Whenevereither condition is recognized, the three PMSM control signals aredriven to zero. In the event of a high trip over-current faultcondition, the power inverter logic has recognized a high over-currentcondition and shuts down the three PMSM control signals until therespective left or right controller logic resets the latch storing thedata indicative of this condition using a fault reset command. In theevent of a low trip over-current fault condition, the power inverter hasrecognized a low over-current condition and drives the three PMSMcontrol signals to zero until the next set of six controller PWM controlsignals are received from the respective power inverter. An over-voltagecondition is recognized by receipt of a controller DC voltage levelsignal from the bias supply/dynamic brake/contactor control. When thissignal is at a pre-determined level, it also drives the three PMSMcontrol signals to zero.

Referring again to FIG. 7, the bias supply/dynamic brake/contactorcontrol serves three functions: (1) the generation of various biasvoltage supplies such that the various deck controller components maysafely operate on a suitable voltage supply; (2) dynamic braking supportor contactor support; and (3) the sensing of various fault conditions.

The bias supply logic uses: (1) a switching mode buck regulator circuitto generate a 15V, DC bias supply level from the 48V, DC battery; (2) acoupled inductor to generate a 5V, DC bias supply level from the 15V, DCbias supply level; (3) and a linear regulator to generate a 3.3V, DCbias supply level from the 5V, DC bias supply level. The bias supplylevels are suitably coupled to the various components of the deckcontroller for power. The bias supply logic is coupled to the 48V, DCthrough an ignition switch, and is also coupled to the 48V, DC batteryeither directly or via an external contactor in an optional embodiment.The bias supply logic may also contain power hold logic which acts tofeedback the generated 15V, DC bias supply level back to the bias supplylogic in order to keep the bias supply logic enabled and generating thebias supply levels in the event the ignition switch is opened. This maybe used to keep the deck controller alive to brake the deck motorsfollowing an opening of the ignition switch.

The contactor is coupled between the 48V, DC battery and the bias supplylogic and acts as a secondary source of power. The main purpose of thecontactor is to open and close the main power for the power inverters,if the contactor is opened it is impossible to drive the motor throughthe ignition only, for safety. Generally, if the ignition switch isopened by the user, the bias supply logic and the remainder of the deckcontroller will lose the 48V, DC voltage level from the battery. Inorder to maintain the bias supply levels when the ignition switch isopened to effectuate a controlled braking of the left and right deckmotors, the contactor and contactor logic provides the battery voltageto the bias supply logic for a limited period of time to power the deckcontroller. The opening and closing of the contactor is controlled bythe controller logic, which has knowledge of the open or closed state ofthe ignition switch via ignition sense logic. A particular advantage ofthe contactor logic is that it also provides reverse current protectionand current leakage protection from the battery.

The dynamic brake logic can implement and control the absorption ofexcess voltage that is pumped back to the battery during regenerativebraking. A dynamic braking resistor is controlled by a dynamic brake PWMsignal to absorb this voltage in lieu of the battery absorbing the load.

The bias supply/dynamic brake/contactor control includes the followingfault sensing capabilities: (1) over-voltage comparator logic thatgenerates an over-voltage fault signal, which indicates whether the DCvoltage from the battery is in an over-voltage condition; (2) controllerDC voltage sensing logic that generates the controller DC voltage levelsignal representative of the DC voltage from the battery; and (3)brake/contactor coil current sensing logic that generates abrake/contactor coil over-current fault signal and a brake/contactorcoil over current signal that respectively represent whether a faultexists due to an over-current condition during dynamic braking orcontactor coil operation and the corresponding current level.

Referring again to FIG. 7, the battery conditioner is coupled betweenthe 48V, DC battery and the bias supply logic, dynamic brake logic andcontactor logic. Generally, the battery conditioning logic comprisessurge limits to prevent the battery inrush when the deck is firstpowered on, electromagnetic interference (EMI) filters to prevent radiointerference, and a capacitor network to limit voltage arching whenfirst powered on.

FIG. 11 illustrates a bubble-state map for the motor control structure.As shown, the motor control has a power up state, an off state, aprecharge state, a slide-mode-control open-loop-ramp state, aclosed-loop FOC-enabled state, a braking state, a faulted state, and aclearing fault state. The slide mode control open loop ramp state is theinitial state of the motor when it is driven to pre-determined inputs.After the rotor speed reaches a predetermined amount (e.g., 900 RPM),the control loop is closed and the control is in the closed loop FOCenabled state, where the FOC algorithms are used to drive the motors.

FIG. 12 illustrates flow charts for the main program flow associatedwith the deck controller in operation. The controllers 530 a and 530 bperform the tasks of processing input/outputs, calculating RPM,Processing SPI messages, and processing state machine. In addition, theleft or master controller processes CAN-bus messages. These processesare run in a predetermined interval, and in this particular embodiment,every 13 ms. In addition, temperature processing and overload protectionprocessing (I²T methods) occurs at a predetermined interval, and in thisparticular embodiment, every second. The remaining process involvesapplication of FOC techniques to drive the motors.

In should be noted that one or more aspects of the control architecturedepicted in FIGS. 8-10 can generally be applied to the fractioncontroller as well, or any other controller involved in driving anelectric motor of the vehicle.

As those skilled in the art would understand and appreciate, theforegoing embodiments of motor drive control may implement numerousdifferent PWM schemes for controlling current through the motor. Whiledual-sided PWM schemes are contemplated, in alternate embodiments,single-sided PWM schemes may also be employed. As understood by thoseskilled in the art, dual-sided PWM schemes (or 4-quadrant switching)utilize pulse-width modulation of switches on both sides of an H-bridgeor 3-phase bridge (for three-phase motors) to effectuate pulse-widthmodulation. In a typical dual-side scheme, each set of switches of thebridge are pulse-width modulated independently such that the variationand overlap between the resulting PWM signals defines the current to theelectric motor. On the other hand, single-sided PWM schemes(two-quadrant switching) pulse-width modulate the switches on one sideof the bridge for controlling the magnitude of the current to theelectric motor, while utilizing the switches on the other side of thebridge to control the direction of current to the electric motor.Single-sided PWM schemes may be beneficial to reduce switching noisewithin the circuits because the switches involved in controlling thedirection of current switch less frequently than the switches involvedin controlling the magnitude of the current.

To illustrate a single-sided or two-quadrant switching scheme, FIG. 13is provided, which is a schematic diagram of a 3-phase bridge comprisingthree switch pairs, S₁ and S₁′, S₂ and S₂′, and S₃ and S₃′. S₁, S₂ andS₃ are on the high-side bus and S₁′, S₂′, and S₃′ are on the low sidebus. The switch pairs are configured to provide respective motor current(I₁, I₂, and I₃) for each of the phases of the motor. In a single-sidedscheme, a positive first phase voltage is supplied to the motor byactivating switch S₂′ in a constantly ON state while switch S₁ ispulse-width modulating. When both S₁ and S₂′ are ON, current I₁increases to drive the motor in a forward direction state. During theperiod where no pulse-width modulation occurs, the current is slowlydecaying (sometimes referred to as free-wheeling) in a short circuitstate. When a negative first phase voltage is applied by activatingswitch S₁′ in a constantly ON state while switch S₂ is pulse-widthmodulating, current I₁ increases to drive the motor in a reversedirection state. Only two switching events occur in a PWM period. Theforegoing results will be similar when only the low side switches aremodulated.

It should be noted that the term “switch” or “switch device” is intendedto include, but not be limited to, any semiconductor or solid statecomponent or device, either singly or in combination with othercomponents or devices, that can control current based on a control inputapplied to the component(s) or device(s). Merely by way of example, suchswitches may include field effect transistors, such as MOSFETS,insulated gate bipolar transistors (IGBTs) or the like. Due to themagnitude of current utilized in electric motors for utility vehicleapplications, MOSFETS or other similar components capable of handlinghigh current levels and resulting heat generation are preferred.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof.

What is claimed is:
 1. A utility vehicle comprising: a plurality ofvehicle systems comprising an accelerator system, a power system, atraction system, and an auxiliary system; a plurality of operatorinterfaces for operating the utility vehicle; a plurality of sensors;and an electric motor control system in communication with the pluralityof vehicle systems, the plurality of operator interfaces, and theplurality of sensors; the traction system comprising: at least onedriven wheel; and at least one electric drive transaxle engaged with theat least one driven wheel; the auxiliary system comprising: an auxiliarymechanism; and an AC electric auxiliary motor engaged with the auxiliarymechanism; the electric motor control system comprising: a tractioncontroller in communication with the accelerator system, at least one ofthe plurality of operator interfaces, at least one of the plurality ofsensors, the power system, the auxiliary system, and the at least oneelectric drive transaxle of the traction system; and an auxiliarycontroller in communication with the traction controller, the powersystem, and the AC electric auxiliary motor, wherein the auxiliarycontroller applies field oriented control to the AC electric auxiliarymotor and controls the AC electric auxiliary motor via at least one DCcontrol technique.
 2. The utility vehicle of claim 1, wherein: at leastone of the plurality of sensors comprises a Hall effect sensor fordetecting a position of a rotor of the AC electric auxiliary motor; andthe auxiliary controller is further in communication with the Halleffect sensor.
 3. The utility vehicle of claim 1, wherein the auxiliarymechanism comprises a cutting blade mechanism.
 4. The utility vehicle ofclaim 1, further comprising a data bus that provides communicationbetween the traction controller and the auxiliary controller.
 5. Theutility vehicle of claim 1, wherein the AC electric auxiliary motorcomprises an AC PMSM motor.
 6. The utility vehicle of claim 1, whereinthe plurality of operator interfaces comprises a left drive lever and aright drive lever, the left drive lever and the right drive leverassociated with the accelerator system.
 7. The utility vehicle of claim6, wherein the plurality of sensors comprises a left drive leverposition sensor associated with the left drive lever and a right drivelever position sensor associated with the right drive lever.
 8. Theutility vehicle of claim 1, wherein the field oriented control comprisessensorless field oriented control.
 9. A utility vehicle comprising: aplurality of vehicle systems comprising an accelerator system, a powersystem, a traction system, and an auxiliary system; a plurality ofoperator interfaces for operating the utility vehicle; a plurality ofsensors; and an electric motor control system in communication with theplurality of vehicle systems, the plurality of operator interfaces, andthe plurality of sensors; the traction system comprising: at least onedriven wheel; and at least one electric drive transaxle engaged with theat least one driven wheel; the auxiliary system comprising: a firstauxiliary mechanism and first AC electric auxiliary motor engaged withthe first auxiliary mechanism; and a second auxiliary mechanism and asecond AC electric auxiliary motor engaged with the second auxiliarymechanism; the electric motor control system comprising: a tractioncontroller in communication with the accelerator system, at least one ofthe plurality of operator interfaces, at least one of the plurality ofsensors, the power system, the auxiliary system, and the at least oneelectric drive transaxle of the traction system; and an auxiliarycontrol system in communication with the traction controller, the powersystem, the first AC electric auxiliary motor, and the second ACelectric auxiliary motor, the auxiliary control system comprising: afirst controller; a second controller; a common interface incommunication with the first controller and the second controller; afirst power inverter in communication with the common interface and thefirst AC electric auxiliary motor; and a second power inverter incommunication with the common interface and the second AC electricauxiliary motor; wherein each of the first controller and the secondcontroller applies field oriented control to the first AC electricauxiliary motor and the second AC electric auxiliary motor and controlsthe first AC electric auxiliary motor and the second AC electricauxiliary motor via at least one DC control technique.
 10. The utilityvehicle of claim 9, wherein the first auxiliary mechanism and the secondauxiliary mechanism each comprises a cutting blade mechanism.
 11. Theutility vehicle of claim 9, wherein the first AC electric auxiliarymotor and the second AC electric auxiliary motor each comprises an ACPMSM motor.
 12. The utility vehicle of claim 9, wherein: at least one ofthe plurality of sensors comprises a Hall effect sensor for detecting aposition of a rotor of the first AC electric auxiliary motor and thesecond AC electric auxiliary motor; and the auxiliary control system isfurther in communication with the Hall effect sensor.
 13. The utilityvehicle of claim 9, further comprising a first data bus that providescommunication between the traction controller and the auxiliary controlsystem.
 14. The utility vehicle of claim 9, further comprising a seconddata bus that provides communication between the first controller andthe second controller.
 15. The utility vehicle of claim 9, wherein thefirst controller of the auxiliary control system is designated as amaster and the second controller of the auxiliary control system isdesignated as a slave that is configured to be subordinate to the firstcontroller.
 16. The utility vehicle of claim 9, wherein the plurality ofoperator interfaces comprises a left drive lever and a right drivelever, the left drive lever and the right drive lever associated withthe accelerator system.
 17. The utility vehicle of claim 16, wherein theplurality of sensors comprises a left drive lever position sensorassociated with the left drive lever and a right drive lever positionsensor associated with the right drive lever.
 18. The utility vehicle ofclaim 9, wherein the field oriented control comprises sensorless fieldoriented control.